A phenomenological model is presented to assess the effects of phase mixing on storage modulus vs. temperature data in polymer blends comprising a continuous glassy matrix and discrete rubbery inclusions. An extension of the Kerner-Dickie model, it is developed for systems of low-dispersed phase content with a moderate degree of intermixing, and compared with experimental data for six blends of polystyrene or lightly hydroxylated polystyrene with poly(ethyl acrylate) at 90/10 and 70/30 w/w compositions. Phase mixing is induced in this system through intercomponent hydrogen bonding. The model successfully represents data for the four blends of lowest interphase content, but fails for the other two. The model can evidently provide a good description of blends where the bulk of each component resides in a pure phase, but fails when the mixed interphase constitutes the majority of the material.